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Hunting the mysterious monopole

Video: Making a monopole

By Eugenie Samuel Reich

THEY seem magical&colon; magnets, every child’s favourite science toy. Two otherwise ordinary lumps of metal draw inexorably closer, finally locking together with a satisfying snap. Yet turn one of them round and they show an entirely different, repulsive face&colon; try as you might to make them, never the twain shall meet.

If magnets seem rather bipolar, that’s because they are. Every magnet has two poles, a north and a south. Like poles repel, unlike poles attract. No magnet breaks the two-pole rule – not the humblest bar magnet, not the huge dynamo at the heart of our planet. Split a magnet in two, and each half sprouts the pole it lost. It seems that poles without their twins – magnetic “monopoles” – simply do not exist.

That hasn’t stopped physicists hunting. For decades they have ransacked everything from moon rock and cosmic rays to ocean-floor sludge to find them. There is a simple reason for this quixotic quest. Our best explanations of how the universe hangs together demand that magnetic monopoles exist. If they are not plain to see, they must be hiding.

Now, at last, we have might have spied them out. The first convincing evidence for their existence has popped up in an unexpected quarter. They are not exactly the monopoles of physics lore, but they could provide us with essential clues as to how those legendary beasts behave.

“These might not be the monopoles of physics lore – but they could provide the first clues as to how those legendary beasts behave”

So what attracts physicists to monopoles? Several things. First, there’s symmetry …